1. Field of the Invention
The present invention relates to a connection structure for a radio frequency circuit, which is suitable for use in receiving converters for satellite broadcasting and the like.
2. Description of the Related Art
A conventional connection structure for a radio frequency circuit will be described with reference to FIG. 13 (hereunder, radio frequency is abbreviated as RF). A printed circuit board 51 is provided with a wiring pattern 52 on one side, and the wiring pattern 52 mounts various electric components (not illustrated) to form a desired RF circuit.
The wiring pattern 52 includes first and second conductors 52a, 52b that are located with a space in between, and a third conductor 52c that passes between the first and second conductors 52a, 52b. 
A grounding pattern 53 for shielding is provided on all the other side of the circuit board 51, which is not illustrated here. The circuit board 51 thus constructed is attached to a frame, in such a manner that the electric components are located inside the frame, and the grounding pattern 53 is exposed outside the frame. The grounding pattern 53 together with the frame plays a role of shielding the electric components.
A jumper member 54 is made up with a pipe-formed shield 55 made of phosphor copper, an insulator 56 molded inside the shield 55, and a jumper line 57 buried in the center of the insulator 56.
The jumper line 57 has a straight base part 57a, and a pair of terminals 57b bent at a right angle to the base part 57a from both ends thereof, thus forming a U-shaped structure. The center of the base part 57a is retained by the insulator 56, and is shielded by the shield 55. Both the ends of the base part 57a and the terminals 57b are exposed from the shield 55.
The jumper member 54 is placed on the side of the grounding pattern 53 of the circuit board 51, which is exposed outside, and the shield 55 is soldered on the grounding pattern 53.
The pair of terminals 57b of the jumper line 57 are inserted through holes 51a of the circuit board 51, and are each soldered to the first and second conductors 52a and 52b. Thus, the jumper line 57 is connected to the first and second conductors 52a, 52b so as to intersect the third conductor 52c. 
In the jumper member 54 used in the conventional connection structure for an RF circuit, since the insulator 56 and the jumper line 57 are molded in the shield 55, the production cost becomes expensive, and this is a problem to be solved.
Further, both the ends of the base part 57a and the terminals 57b are exposed outside the shield 55, and when the jumper member 54 is mounted on the circuit board 51, both the ends of the base part 57a and the terminals 57b are exposed from the grounding pattern 53, which deteriorates the RF characteristics.
Accordingly, it is an object of the present invention to provide a connection structure for an RF circuit that exceeds in the RF characteristics at a low cost.
According to one aspect of the invention, the connection structure for an RF circuit is provided with a circuit board that mounts electric components on a wiring pattern provided on one side thereof to form a desired RF circuit, a grounding pattern provided on another side of the circuit board, and a jumper member provided on the other side of the circuit board. The jumper member is made up with a boxed-shaped cover with a lower side open, an insulating base contained inside the cover, and a jumper line of which both ends are projected downward from a lower side of the insulating base in a state that the jumper line is positioned by the insulating base. The jumper line has a base part that is positioned by the insulating base, and is placed inside the cover to be electrically shielded, and terminals projected downward from the lower side of insulating base. The wiring pattern includes first and second conductors and a third conductor that passes between the first and second conductors. As to the jumper member provided on the other side of the circuit board, the insulating base having positioned the jumper line is mounted on the circuit board. The terminals are inserted through the circuit board to be connected to the first and second conductors in a state that the jumper line intersects the third conductor. And, the cover is attached to the circuit board in a state that the lower ends of cover are put into contact with the grounding pattern.
According to another aspect of the invention, a whole circumference of the cover is soldered to the grounding pattern.
According to another aspect of the invention, the jumper line has a straight base part and a pair of terminals that are bent from both ends of the base part. The insulating base has a longitudinal through hole, and the base part is inserted through the through hole, whereby the jumper line is positioned and retained.
According to another aspect of the invention, the jumper line has a straight base part and a pair of terminals that are bent from both ends of the base part. The base part is placed in a groove provided on an upper part of the insulating base, whereby the jumper line is positioned.
According to another aspect of the invention, the jumper line has a straight base part and a pair of terminals that are bent from both ends of the base part. The terminals are inserted through vertical holes provided on the insulating base, whereby the jumper line is positioned and retained.
According to another aspect of the invention, the circuit board is attached to an open part provided to one side of a frame, the electric components are located inside the frame, and the grounding pattern and the jumper member are exposed outside the frame.
According to another aspect of the invention, a feeder horn is attached to the grounding pattern to be located outside the frame to form a receiving converter for satellite broadcasting.